Color television tube having venetian blind-type grid



y 1963 w. VEITH ETAL 3,090,890

COLOR TELEVISION TUBE HAVING VENETIAN BLIND-TYPE GRID Filed July 7, 1960 2 Sheets-Sheet 1 May 21, 1963 w. VEITH ETAL 3,090,890

COLOR TELEVISION TUBE HAVING VENETIAN BLIND-TYPE GRID Filed July 7, 1960 2 Sheets-Sheet 2 Fig.2

3,090,8J COLOR TELEVISION TUBE HAVING VENETIAN BLEND-TYPE GRID Werner Veith, Munich, and Hinrich Heynisch, Grafelfing, near Munich, Germany, assignors t0 Siemensdz Halske Aktiengesellschatt, Berlin and Munich, a corporation of Germany Filed July 7, 1960, Ser. No. 41,395 Claims priority, application Germany Sept. 25, 1959 4 Claims. (Cl. 315-41) This invention is concerned with a color television tube.

The following considerations will aid the understanding of the invention:

An electron beam tube for reproducing color television pictures has been proposed before, comprising, in addition to the focusing and deflection means which are customarily employed in the case of monotone picture tubes, at least one grid arranged in the beam path ahead of and parallel to the screen electrode, such grid consisting of narrow mutually spaced apart metallic strips or slats extending in the manner of a Venetian blind and being inclined to the tube axis so as to practically conceal part of the view in the direction of the tube axis, as in the case of an incompletely opened Venetian blind, electrons which are easily influenced appearing in the range of the Venetian blind grid which are on the screen side deflected from the paths by the acceleration field of the screen electrode and thereby focused so that they are, by further means which periodically affect their acceleration (color selection means), successively pictured upon individual color strips of an elementary group of color strips of the screen which is allocated to a gap formed by two respectively neighboring metallic slats. The prior picture tube provides for the color selection a grid arranged between the Venetian blind grid and the screen electrode and extending parallel to the latter, such grid being made of parallel disposed galvanically interconnected wires, the individual grid wires being with uniform grid division (pitch) respectively disposed in a plane formed by edges of the metallic slats of the Venetian blind grid facing the screen electrode and extending perpendicular thereto. The electrons emerging from the gaps of the Venetian blind grid are in operation affected by the iield of this grid, due to a high frequency color selection voltage connected thereto, so that they alternately reach the proper color strip belonging to the corresponding elementary group.

Technical difficulties are experienced in the disposition of the color selection grid, with respect to its division (pitch), relative to the Venetian blind grid in the screen electrode which is subdivided into elementary groups. The object of the invention is to avoid these difliculties to a far reaching extent, that is, to reduce the amount of adjustment work and possible error sources, by a considerable simplification of the auxiliary color selection means.

This object is realized, in connection with the initially described electron beam tube for reproducing color television pictures, by arranging, as seen in the beam direction, in back of a cylindrical lens electrode and ahead of the Venetian blind grid, a further grid (color selection grid) extending parallel thereto, such further grid comprising parallel tensioned wires extending in vicar of the division of the Venetian blind grid and the elementary groups of the screen electrode not necessarily in a uniform structure and having a potential applied thereto which is by a few volts different from that applied to the Venetian blind grid, so that the slow electrons are in the range of the Venetian blind grid, by a high frequency color selection voltage applied to the color selection grid, with diiferent strength deflectable with respect to the ice screen electrode according to the respectively appropriate color strips of the elementary groups.

Accordingly, as compared with the previously proposed structure, the auxiliary color selection grid is in the beam path disposed not in back but ahead of the Venetian blind grid, that is, at the side facing the cathode. This arrangement has as contrasted with the first noted grouping the considerable advantage, first, that the grid can have an irregular structure, that is, that it need not be matched to and adjusted to the subdivision of the Venetian blind grid, and second, that only relatively low volt-ages are required for eifecting its control. It is moreover important for the imaging mechanism that this grid is not positioned in the imaging path of the electrons.

The various objects and features of the invention will appear from the description which is rendered below with reference to the accompanying purely schematic drawings, in which:

FIGPI shows the spatial arrangement of the color selection grid with respect to the remaining electrodes contained in the tube; and

FIG. 2 represents the potential conditions in the space between the screen electrode and the color selection grid, for the case of slowed electrons, that is, without the use of secondary electrons.

In FIG. 1, numeral 1 indicates the tube envelope and 2 the course of the electron beam which is in customary manner produced by means of a generating system 3 comprising, among others, a cathode, a control electrode (Wehnelt cylinder), and an acceleration electrode, the

, beam being thus accelerated and by suitable means focused. The beam is by means of a deflection device, for example, a magnetic deflection device positioned at the transition irom the neck to the cone part of the tube, deflected so that it describes a rectangular raster in a plane extending approximately parallel to the tube base. The beam is, however, by means of the cylindrical lens electrode 4 in cooperation withthe acceleration anode in the beam generating system, slowed down, focused and deflected in a direction parallel to the tube axis, so that it enters approximately perpendicular into the grid plane of the color selection grid 6 and the grid 5 which is constructed in the fashion of a Venetian blind. The color selection grid 6 consists of tensioned wires extending in a common plane and interconnected galvanically; the subdivision structure (pitch) of these grid Wires is independent of that of the Venetian blind grid. Spaced from the latter is the fluorescent screen 7 which is provided with conductive support 8, high voltage being placed on the screen so as to accelerate to the required energy the electrons leaving the Venetian blind grid with low initial velocity.

FIG. 2 shows in partial view the potential course between the color selection grid 6, the Venetian blind grid 5, and the screen electrode 7, 8, assuming that the electrons accelerated by the beam generating system are, in the range of the Venetian blind grid, merely slowed down to about 0 volt and cause, without the release of secondary electrons, responsive to appropriate successive acceleration, the excitation of the fluorescent screen. The metallic strips or slats of the Venetian blind grid 5 are for this purpose with respect to the cathode at a negative potential of, for example, 20 v., so that, as already mentioned, no electrons (primary electrons) can reach them. The color selection grid 6 receives a positive potential of, for example, +20 volts, that is, it will be by the same amount more positive than the Venetian blind grid is with respect to the cathode potential more nega tive. This causes, in the region approximately ahead of the individual gaps formed in the Venetian blind grid, appearance of saddle points in the potential field, that is,

between the color selection grid 6 and the metallic strips 5, which efiect slowing down of the electron beam. The electrons assume due to slowing down at the saddle points very low velocity, about +2 volts, and are thereupon again accelerated by the high potential of the picture screen and thus focused to the individual color strips owing to the deflection which occurs thereby. Accordingly, the potential of the Venetian blind grid is during operation always constant, while high frequency color selection voltage is solely connected to the color selection grid. However, the potential of the color selection grid may conversely be held constant and the potential of the color selection voltage may be correspondingly connected to the Venetian blind. It may likewise be advantageous to vary both potentials of the respective electrodes approximately symmetrical to the cathode potential in accordance with opposite values corresponding to the color selection voltage.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

We claim:

1. An electron beam tube for reproducing color television pictures, having deflection and focusing means customarily utilized in monotone picture tubes and having a cylindrical lens electrode, and having at least one grid arranged ahead of and extending in parallel with the picture screen, said grid consisting of relatively narrow metallic strips which are mutually spaced apart to form gaps therebetween and which are inclined to the tube axis in the manner of the slats of an incompletely opened Vene- (tian blind so as to practically shut off continuity in the direction of the tube axis, wherein easily influenced elec trons appear in the range of the Venetian blind grid which are upon the screen side thereof deflected from their path by the acceleration field of the screen electrode and thereby focused so that they are by color selection means which periodically affect the acceleration thereof successively pictured upon individual color stripscf an elementary group of color strips of the screen which group is allocated to a gap formed by respectively neighboring metallic strips, comprising a further color selection grid arranged as seen inlthe beam direction in back of said cylindrical lens electrode and ahead of said Venetian blind grid and parallel thereto, said further color selection grid being formed of parallel extending tensiOned Wires not necessarily extending regularly with respect to the division of the Venetian blind grid and the elementary groups of the screen electrode and having a common potential connected thereto which is by a few volts difierent from that carried by the Venetian blind grid, whereby the slow electrons are in the range of the Venetian blind grid by a high frequency color selection voltage additionally connected to the color selection grid with different strength deflected to the screen electrode in accordance with the respective color strips of the elementary groups.

2. An electron beam tube according to claim 1, wherein the Venetian blind grid is substantially at cathode potential, the potential of the color selection grid being thereby more positive by as many volts as the potential of the Venetian blind grid is more negative than the cathode potential, whereby saddle points are created in the region of the Venetian blind grid in which is effected a slowing down of the electrons to only a few volts velocity.

3. An electron beam tube according to claim 2, wherein the color selection voltage is connected to one of the References Cited in the file of this patent UNITED STATES PATENTS Kallm-an Nov. 11, 1952 Francken Nov. 12, 1957 

1. AN ELECTRON BEAM TUBE FOR REPRODUCING COLOR TELEVISION PICTURES, HAVING DEFLECTION AND FOCUSING MEANS CUSTOMARILY UTILIZED IN MONOTONE PICTURE TUBES AND HAVING A CYLINDRICAL LENS ELECTRODE, AND HAVING AT LEAST ONE GRID ARRANGED AHEAD OF AND EXTENDING IN PARALLEL WITH THE PICTURE SCREEN, SAID GRID CONSISTING OF RELATIVELY NARROW METALLIC STRIPS WHICH ARE MUTUALLY SPACED APART TO FORM GAPS THEREBETWEEN AND WHICH ARE INCLINED TO THE TUBE AXIS IN THE MANNER OF THE SLATS OF AN INCOMPLETELY OPENED VENETIAN BLIND SO AS TO PRACTICALLY SHUT OFF CONTINUITY IN THE DIRECTION OF THE TUBE AXIS, WHEREIN EASILY INFLUENCED ELECTRONS APPEAR IN THE RANGE OF THE VENETIAN BLIND GRID WHICH ARE UPON THE SCREEN SIDE THEREOF DEFLECTED FROM THEIR PATH BY THE ACCELERATION FIELD OF THE SCREEN ELECTRODE AND THEREBY FOCUSED SO THAT THEY ARE BY COLOR SELECTION MEANS WHICH PERIODICALLY AFFECT THE ACCELERATION THEREOF SUCCESSIVELY PICTURED UPON INDIVIDUAL COLOR STRIPS OF AN ELEMENTARY GROUP OF COLOR STRIPS OF THE SCREEN WHICH GROUP IS ALLOCATED TO A GAP FORMED BY RESPECTIVELY NEIGHBORING METALLIC STRIPS, COMPRISING A FURTHER COLOR SELECTION GRIP ARRANGED AS SEEN IN THE BEAM DIRECTION IN BACK OF SAID CYLINDRICAL LENS ELECTRODE AND AHEAD OF SAID VENETIAN BLIND GRID AND PARALLEL THERETO, SAID FURTHER COLOR SELECTION GRID BEING FORMED OF PARALLEL EXTENDING TENSIONED WIRES NOT NECESSARILY EXTENDING REGULARLY WITH RESPECT TO THE DIVISION OF THE VENETIAN BLIND GRID AND THE ELEMENTARY GROUPS OF THE SCREEN ELECTRODE AND HAVING A COMMON POTENTIAL CONNECTED THERETO WHICH IS BY A FEW VOLTS DIFFERENT FROM THAT CARRIED BY THE VENETIAN BLIND GRID, WHEREBY THE SLOW ELECTRONS ARE IN THE RANGE OF THE VENETIAN BLIND GRID BY A HIGH FREQUENCY COLOR SELECTION VOLTAGE ADDITIONALLY CONNECTED TO THE COLOR SELECTION GRID WITH DIFFERENT STRENGTH DEFLECTED TO THE SCREEN ELECTRODE IN ACCORDANCE WITH THE RESPECTIVE COLOR STRIPS OF THE ELEMENTARY GROUPS. 